This application is a 35 USC 371 application of PCT/DE 01/00003 filed on Jan. 5, 2001.
1. Field of the Invention
The invention is directed to a fuel injection valve for internal combustion engines.
2. Description of the Prior Art
One fuel injection valve of the type with which this invention is concerned is known from German Published, Nonexamined Patent Application DE 196 08 575. On the end toward the combustion chamber of the valve member, a substantially conical tip is formed. This tip is divided into two portions; the tip cone angle of the outer portion, toward the combustion chamber, is greater than that of the inner portion, toward the valve member. As a result, an encompassing annular edge is embodied as a sealing face on the jacket face of the valve member tip.
The valve member is disposed in a bore, embodied as a blind bore, and the closed end, toward the combustion chamber, is embodied as a valve seat, which substantially has a conical shape. At least one injection opening is embodied in the valve seat and connects the interior of the valve with the combustion chamber, when the valve member is lifted from the valve seat.
In the closing position of the fuel injection valve, the valve member with its valve sealing face comes to rest on the valve seat. The cone angle of the valve seat is dimensioned such that the valve member is seated on the valve seat essentially only with its annular edge. On the one hand, this produces good sealing of the pressure chamber from the injection openings, but on the other it raises the problem that because of the high pressure per unit of surface area, deformations of the valve member and valve seat occur over time. The annular edge and/or the valve seat deform, causing the effective seat diameter of the valve member to change. As a result, the effective flow cross section of the fuel injection valve also changes, as does the size of the faces on the valve member that are subjected to pressure, which adversely affects the course of fuel injection and the injection precision.
The fuel injection valve of the invention has the advantage over the prior art that the part of the valve member tip bearing the valve sealing face is embodied as a yielding annular collar, and as a result in the closing position of the valve member, the part bearing the valve sealing face, after an initial line contact, rests two-dimensionally on the valve seat. The outer edge of the annular collar defines a fixed seat diameter. Because of the increasing bearing area of the valve member on the valve seat, a relatively small pressure per unit of surface area exists in the region of the valve seat, leading to less wear in this region. Thus the seat diameter remains constant over the service life of the fuel injection valve.
In an advantageous feature, the valve sealing face is partly undercut by the annular groove, so that the annular collar is embodied in liplike fashion to an increased extent, and the deformation work of the annular collar is reduced. By varying the shape of the annular groove, the yielding of the annular collar can be adapted to the applicable material comprising the valve member and the valve body.